Scientists say that reinfections after initial illness caused by the SARS-CoV-2 virus are possible, but so far have characterised them as rare. Fewer than 50 cases have been substantiated worldwide, according to a global reinfection tracker, BNO News.
According to the NBC, five of such cases have been substantiated in the United States, including two detected in California in late January.
While the number sounds insignificant, experts warn that people with COVID-19 may continue to test positive for several months without being sick or infectious.
“A reinfection is confirmed when testing shows that each virus’ genetic makeup is different to a degree which cannot be explained through in-vivo evolution,” experts say.
While experts agree that cases of COVID-19 reinfection are very difficult to ascertain, they suggest that specialised teams are needed to do the work, or a core lab.
Such cases are different from instances of so-called long-haul COVID-19, in which the original infection triggers debilitating symptoms that linger for months and viral particles can continue to be detected.
“Reinfection occurs when a person is infected with COVID-19, clears that strain and is infected again with a different strain,” scientists say.
The guidelines suggested by the Centres for Disease Control and Prevention call for investigating for possible reinfection when someone tests positive for COVID-19 at least 90 days after an original infection (or at least 45 days for “highly suspicious” cases).
CDC had said: “CDC is aware of recent reports of suspected cases of SARS-CoV-2 reinfection among persons who were previously diagnosed with COVID-19 [1–3].
“There is currently no widely accepted definition of what constitutes SARS-CoV-2 reinfection and the reports use different testing methods, making reinfection diagnosis difficult.
“To develop a common understanding of what constitutes SARS-CoV-2 reinfection, CDC proposes using both (1) investigative criteria for identifying cases with a higher index of suspicion for reinfection and (2) genomic testing of paired specimens.
Confirmation of reinfection requires genetic sequencing of paired samples from each episode to tell whether the genomes involved are different, NCDC says.
As reported by the Washington Post, mutated virus may reinfect people already stricken once with COVID-19
Quoting a preliminary data presented last week, the medium reported that the trial of an experimental coronavirus vaccine detected that people who have recovered from infections are not completely protected against a variant that originated in South Africa and is spreading rapidly.
“The finding, though far from conclusive, has potential implications for how the pandemic will be brought under control, underscoring the critical role of vaccination, including for people who have already recovered from infections,” it stated.
Reaching herd immunity — the threshold when enough people achieve protection and the virus can’t seed new outbreaks — will depend on a mass vaccination campaign that has been constrained by limited supply.
Reacting to a preliminary finding from the South African vaccine trial, director of the United States National Institute of Allergy and Infectious Diseases, Anthony S. Fauci, said, “The level of immunity that you get from natural infection — either the degree of immunity, the intensity of the immunity or the breadth of immunity — is obviously not enough to protect against infection with the mutant.”
Also, peer-reviewed journal, BMJ, notes that with most coronaviruses, recovery confers a degree of immunity to reinfection. But a small number of patients have caught COVID-19 for a second time.
The online journal states, “Other things being equal, we can expect to see—even without this new variant (the UK-identified B117)—repeat infections by about now anyway,” says Paul Hunter, professor in medicine at the University of East Anglia.
There are four types of endemic coronaviruses (229E, NL63, OC43, and HKU1) that regularly circulate through humans, causing the majority of respiratory tract infections. Infection with any of them can lead to immunity of differing lengths, typically lasting for at least a year or two, according to Joël Mossong, the head of epidemiology and microbial genomics at the Luxembourg National Health Authority. “You do get reinfected eventually, but not every year,” he says.
But SARS-CoV-2 is an entirely new type of coronavirus and the question of immunity is one of the biggest unknowns. Whether infection confers immunity to reinfection “is uncertain,” wrote Newcastle University academics in a paper published in the Journal of Infection in December 2020.
An early study by Public Health England, indicated that antibodies provide 83% protection against covid-19 reinfections over a five month period. Out of 6614 participants, 44 had “possible” or “probable” reinfections.2
Worldwide, 31 confirmed cases of covid-19 reinfection have been recorded, although that could be an underestimate from delays in reporting and resource pressures in the ongoing pandemic.
“We know that reinfections with SARS-CoV-2 can happen,” says Ashleigh Tuite, assistant professor at the University of Toronto’s Dalla Lana School of Public Health. “The bigger question is: if reinfections are going to happen, how frequently are they happening?”
With attention focused on vaccine rollout and tracking the spread of new variants of covid-19, little work is being done to find out. “If they’re happening a lot, but they’re happening in the context of being less severe, we’re not going to see them unless we design a study that actively tries to figure that out,” says Tuite.
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